Method of forming refractory coating on steel frame

ABSTRACT

This invention provides a method for forming a refractory coating on a column or beam made of steel, the method comprising the steps of adhering panels directly or indirectly to the surface of the column or beam with a specific space between the panels and the column or beam and placing a self-hardening refractory composition into the space. The method of this invention is free from the drawbacks of conventional methods.

TECHNICAL FIELD

This invention relates to methods for forming refractory coatings oncolumns or beams made of steel, and provides methods for applyingself-hardening and fire-resistant compositions to columns or beams madeof steel with extreme ease and reliability to produce refractorycoatings outstanding in function.

BACKGROUND ART

Refractory coating methods considered preferable are those capable offulfilling the following requirements:

(i) giving refractory coating layers as thin as possible which resultsin increasing of living space in the building;

(ii) producing refractory coating layers as lightweight as possiblewhich serve to mitigate the weight load to be supported by the lowerfloors of a high-rise building;

(iii) forming stable refractory coating layers;

(iv) giving refractory coatings which can exhibit good functions in theinterface between the steel element and the coating, more specificallythose which are unlikely to peel or flake in the interface therebetween,particularly when wetted or heated;

(v) being easy to carry out and capable of easily applying thecomposition even to connections between the bases to be coated;

(vi) giving coating layers which can exhibit the desired fire resistancewithin a short time after application;

(vii) applying the composition without scattering the same about thesurrounding, hence without staining the environment;

(viii) using compositions which are easy to transport;

(ix) forming coating layers which develop no crack;

(x) requiring a small number of steps;

(xi) comprising the steps which are easy to perform;

(xii) being economical, etc.

The methods heretofore known for forming refractory coatings on steelelements include the PC method, spraying method, troweling method andconcrete-placing method. The spraying method is subgrouped into dry orsemi-wet spraying method and wet spraying method. These conventionalcoating methods have their own features but suffer drawbacks.

The molding plate method employs molding plates and has the followingadvantages and disadvantages. The advantages are as follows: (1) givingcoatings which have constant quality because of use of molded or shapedplates manufactured in plants, not depending on the skills of operators,(2) enabling the completion of operation at a time even on bases whichrequire 3 hours' fire resistance without involving repeated operations,(3) having the efficiency in work reduced to a lesser extent by theabsence of one operator from a team usually of 3 or 4 operators than thespraying method, (4) effectively preventing the pollution from occuringdue to the scatter of the composition about the environment by the wind,(5) achieving good efficiency in work because of the operation involvingno scatter of composition in the environment. The disadvantages include(1) the need to study the layout and workability when setting moldedplates to a complex place containing diverse kinds of steel elements andnumerous connections as in elevator shafts and staircases which requirecutting and adhering of shaped plates and like cumbersome labors,thereby reducing the efficiency in work, (2) the necessity of removingthe adhesive forced out from between the shaped plate and the surface ofthe base when placing the shaped plates to nooks like return ducts as inelevator shafts and ceilings in order to prevent the adhesive forced outfrom being strewn in the environment, and (3) the need to use anadhesive in larger amounts to assure reliable adhesion, considering thatthe adhesive should not be applied in excess amount to the joint betweenthe shaped plates when adhering shaped plates to steel elements andjoining shaped plates to one another, in order to prevent undesirableshrinkage of the joint from occuring due to the vaporization of thesodium silicate during the hardening of the adhesive, the excessadhesive being unnecessary because of shaped plate units havingrelatively small size and involving low stress due to the heatdistortion and narrow joints between shaped plates.

The PC method involves the use of precast concrete and has theadvantages of saving the labor in construction site because of use ofprefabricated blocks and panels and also being suitable for columns orpillars owing to the hard surface finish. On the other hand, the methodpossesses the drawbacks of involving the use of precast concreteelements which are cumbersome to handle in construction site because ofthe great weight; encountering difficulties in coping with theinterlayer displacement of concrete blocks which would occur due to thehigh rigidity and hardness thereof, depending on the mode of applicationof blocks; and tending to form a layer of great thickness (low in fireresistance and heat insulation per unit thickness).

The spraying method is practiced by spraying coating compositions havingan indeterminate form. The semi-wet spraying method uses a dry powderycomposition with a low water content which is forced by air into thenozzle in the forward end of the spray to mix with water therein. Thewet spraying method employs a liquid coating composition which isprepared by kneading with water and which is forced out by a pump. Theformer method is inexpensive and uses a spray device which islightweight and easy to handle, but the method has the defects of (1)requiring thorough masking to prevent the scatter of the composition inspraying, (2) giving a layer which would peel if exposed to rain beforebeing dried after application, (3) tending to form a layer irregular inquality without adequate quality control, (4) producing a layersusceptible to damage by ductwork or the like performed afterapplication because of the soft layer formed and (5) involving the needto spray a finishing agent over the surface of the layer to prevent dustfrom evolving from the surface of the layer after hardening, dependingon applied surfaces. The wet spraying method frequently uses a mixtureof rock wool, cement and water and has the advantages of using coatingcompositions which can be pumped up to high-floor locations, leading todecrease in lifting costs and which is amenable to a base having acomplicated shape. Nevertheless the method possesses the drawbacks ofusing coating compositions which involve difficulties in coping with thescatter of the composition in the environment and in controlling thequality, particularly the thickness of coating layer, and which requirea considerable time in forming a coating with the desired hardness. Themethod further poses the problems of strewing the composition,consequently smearing the surrounding inside and outside the building;being carried out in poor working conditions; producing layers havinglow adherence to steel elements and poor corrosion resistance.

The troweling method is conducted by skillful plasterers usinghand-trowels. The method can produce layers over bases of any shape andgive jointless coating and pleasing finish, but provides coatings proneto develop cracks. Further the method involves an extremely lowefficiency in work.

The concrete-placing method is performed by literally depositingconcrete which is usally lightweight. The method has the advantages ofusing concrete having lightweight properties and high adherence tosteel. The method suffers the shortcomings of giving coatings tending todevelop cracks and thus essentially needing repair to restore thecracked portions, which presents complicated problems, such asdifficulties in placing concrete into the cracks and in edge cutting,etc.

The conventional methods stated above have further drawbacks in respectof the materials used. The use of concrete materials results in layerswhich undergo marked contraction during hardening due to hydration ofconcrete, thereby involving low dimensional stability and the like. Rockwool and cement materials tend to produce coatings which are soft andwhich give off dust to a great degree. The method using molded platesrequires additional use of adhesives which are cumbersome to handle.Plasters such as cement plaster, gypsum plaster, etc. need expandedmetal lath bases. In addition, these compounds all require treatment ofsteel elements for corrosion prevention.

An object of this invention is to provide a method for formingrefractory coatings free from the drawbacks of the foregoingconventional methods.

Another object of the invention is to provide a method for givingcoatings having higher fire resistance than those formed by conventionalmethods.

DISCLOSURE OF THE INVENTION

This invention provides a method for forming a refractory coating to acolumn or beam made of steel, the method comprising the steps of (1)adhering panels directly or indirectly to the surface of the column orbeam with a specific space between the column or beam and the panels and(2) placing a self hardening refractory composition into the space wherethe composition hardens into a layer integrally united with the columnor beam and the panels. Preferably the method of this invention iscarried out by using a self-hardening composition comprising as the maincomponents (A) water-soluble alkali silicate, (B) a hardening agent forthe water-soluble alkali silicate, and (C) a material containing boundwater or a material capable of absorbing heat when heated and optionally(D) a metallic foaming agent (and when required, (E) a foamingstabilizer).

The method of this invention can overcome the drawbacks of theconventional methods by using the self-hardening composition, preferablythe self-hardening composition comprising the components (A) to (E).More specifically, the deficiencies of conventional methods can beobviated as follows. The defects attendant on use of molded plates existin no way with the method of this invention which employs no moldedplates. The method of this invention employs adhesives but only in smallamounts and thus is virtually free of the problems resulting from theuse of adhesives. The difficulties arising from the PC method are notencountered with the method of the invention which uses no concrete. Theproblems of the dry spraying method using dry powder are not posed bythe method of the invention which uses no dry powder. The method of theinvention requiring no spraying can harden the surface of the layer to aspecific extent in a short time and thus has no drawback in this respectfound in the wet spraying method. The method of the invention is notconducted by plasterers and thus suffers no defect found in thetroweling method. The method of the invention produces coatings whichdevelop no crack unlike the concrete-placing method and thereforerequires no reinforcement.

Further, the layer of composition used in the method of the inventioncauses little or no contraction during the hardening reaction as inconcrete, and is not as soft as those produced by rock wool-cement typecompositions, consequently evolving no dust. The method of the inventionusing no molded plate requires no adhesives for adhering the same unlikethe shaped plate method. The method of the invention does notnecessarily use an expanded metal lath base nor involves anti-corrosiontreatment of iron element. As described hereinbefore, the method of theinvention can overcome all drawbacks of the conventional refractorycoating methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b show an embodiment of the method according to thisinvention using a wide-flange section steel piece, and FIG. 2 anembodiment of the method according to this invention using a squaresteel piece.

FIGS. 3-7 illustrate the steps in the method of the present invention.

BEST EMBODIMENTS OF THE INVENTION

This invention will be described below in more detail with reference tothe drawings. FIG. 1 shows an embodiment of the method of the inventionusing a wide-flange section steel piece. FIG. 1 indicates a perspectiveview at (a) and a cross sectional view at (b) taken on line A--A'. InFIG. 1, indicated at 1 are corner bead; 2, panel; 3, refractoryself-hardening composition; 4, spacer; 5, wide-flange section steelpiece; 6, backer; and 7, adhesive. First, backers 6 are adhered to thewide-flange section steel piece 5 to make the contour square. Thenspacers 4 are attached to the sides of the steel piece 5 by applying anadhesive 7 to the spacers 4 and the steel piece 5 with specific spacingtherebetween so that the length of the spacers corresponds to thethickness of a layer of selfhardening composition 3. A pair of panels 2are joined to the outer ends of the spacers with the adhesive 7 and atthe same time another pair of panels are attached to the first-mentionedpair to form an enclosure as shown in FIG. 1. The enclosure isreinforced in corners with corner beads 1. The self-hardeningcomposition 3 is poured into the space between the panels 2, wide-flangesection steel piece 5 and the backer 6 to harden therein.

Wide-flange section steel pieces useful in this invention can be any ofthose heretofore used. Usable as spacers in this invention are a widerange of those known in the art including, for example, both organic andinorganic spacers. Examples of the former are corrugated boards,plywoods, insulation boards and the like. Examples of the latter arewire nettings, gypsum boards, asbestos cement slates, cemented excelsiorboards, pulp cement flat sheets, hard boards and the like. The size ofthe spacers may be suitably determined according to the wide-flangesection steel piece. Useful adhesives are not particularly limited andcan be any of organic and inorganic adhesives, examples of the formerbeing epoxy resins and the like and examples of the latter being thoseof water glass-type and phosphate-type and the like. The spacers serveas supporters for forming space between the steel piece and the panelsand are inoganic and relatively high in fire resistance and heatinsulation. Examples of useful spacers are calcium silicate plates,foamed lightweight concrete plates, mortar plates, gypsum plates, etc.The size of the spacers in general is approximately 20 mm×20 mm. Thelength of the spacers is determined depending on the thickness of alayer of self-hardening composition, for example ranging from about 10to about 40 mm. The spacers act as supporters not only for the panelsbut also for the self-hardening composition.

While serving as the formwork into which the self-hardening compositionis poured, the panels also constitute the finish surface of therefractory coating. Panels of adequate materials are selected and usedaccording to the thickness of self-hardening composition layer. Forexample, if the self-hardening composition is applied to a thicknesssufficient to meet the fire resistance requirement, the kind of panelsused may be adequately determined over a wide range without particularattention to the fire resistance of panels used. Specific examples ofuseful panels are gypsum boards, asbestos cement slates, cementedexcelsior boards, pulp cement flat sheets, plywoods, particle boards,hard boards, etc. Preferred panels are those high in hardness and heatresistance and relatively small in thickness such as asbestos cementslates, decorated asbestos cement slates, decorated composite panels,etc.

The self-hardening compositions to be used in this invention are suchthat the composition is mixed with water to give a mixture which becomeshardened after standing at ambient temperature. Typical examples of suchcompositions are those comprising (A) water-soluble alkali silicate, (B)a hardening agent for the water-soluble alkali silicate and (C) amaterial containing bound water or a material capable of absorbing heatwhen heated, and those comprising the components (A) to (C) and (D) ametallic foaming agent and (E) a foaming stabilizer.

Water soluble alkali silicate is used as the component (A) for theself-hardening composition to be used in the method of this invention.Examples of the alkali forming the component (A) are lithium, sodium,potassium, rubidium and like alkali metals and quaternary ammoniumcompounds among which sodium, potassium and the like are inexpensive,easily available and significantly effective in promotion of foaming andhardening, hence desirable. Insofar as the component (A) is soluble inwater, there is no limitation on its composition and the mole ratio ofalkali oxide to SiO₂. However, it is preferred that the mole ratio beabout 1.5 to about 4.0, particularly about 1.8 to about 3.0. With themole ratio of 1.8 to 3.0, a foamed body is formed with significantlyhigh water resistance and great mechanical strength. The components (A)can be used singly, or at least two of them are usable in admixture, inthe form of either powder or an aqueous solution with good results. Forthe ease of preparation of paste, an aqueous solution is preferred whichhas a solids concentration of about 10% or more, usually about 10 toabout 50%. In this case, a pasty composition can be easily prepared bymerely mixing the aqueous solution with the other components. Theresulting paste composition shrinks to a relatively lower degree duringhardening.

The hardening agent for water-soluble alkali silicate used as thecomponent (B) in this invention is at least one material selected fromthe group consisting of hydraulic cements, silica dusts, zinc oxides,acidic metallic oxides, bivalent or higher valent metal salts of higherfatty acids, bivalent or higher valent metal salts of water-soluble highpolymers having carboxyl, phosphates, borates, sulphates of bivalentmetals and sulphites of bivalent metals. Examples of hardeningcomponents are as follows. Useful hydraulic cements include hydrauliclime, natural cement, portland cement, alumina cement and like cementssingly used, and lime containing cement, blast furnace cement, silicacement, fly ash cement, masonry cement, high-sulphate cement and likecements used in mixture. Typical examples of the bivalent or highervalent metal salts of higher fatty acids are zinc salts, aluminum salt,calcium salt, barium salt, magnesium salt and nickel salt of stearicacid and palmitic acid, etc. The bivalent or higher valent metal saltsof water-soluble high polymers containing carboxyl are those formed ofwater soluble high polymers and metals, examples of the water solublehigh polymers being alginic acid, polyacrylic acid, polymethacrylicacid, cellulose derivative, alkyd resin, aminoalkyd resin and the like,and examples of bivalent or higher valent metals being those selectedfrom Zn, Cu, Ca, Mg, Be, Sr, Ba, Al, Ti, Zr, Sb, Cr, Mo, W, Sb, Mn, Fe,Co, Ni, and V. Silica dust is produced as a by-product in thepreparation of silicon and silicon alloy by anelectrothermal-metallurgical process. Preferred examples of silica dustare those having a particle size of about 0.1 to about 1.0μ, a specificsurface area of about 5 to about 50 m² /g and bulk specific gravity ofabout 0.1 to about 0.3 and containing 60% by weight, preferably at leastabout 80% by weight, of SiO₂. Examples of acidic metallic oxides are Cr₂O₃, MnO, Mn₃ O₄, FeO, CoO, PbO, etc. Examples of phosphates are aluminumphosphate, calcium phosphate, zinc phosphate, thallium phosphate,strontium phosphate, barium phosphate, magnesium phosphate, manganesephosphate, etc. Examples of borates are zinc borate, magnesium borate,manganese borate, lead borate, nickel borate, calcium borate, etc.Examples of sulphates of bivalent metals are magnesium sulphate, zincsulphate, calcium sulphate, barium sulphate, etc. Examples of sulphitesof bivalent metals are calcium sulphite, magnesium sulphite, zincsulphite, copper sulphite, etc.

A material containing bound water or material capable of absorbing heatwhen heated is used as the component (C) in this invention. The term"material containing bound water or material capable of absorbing heatwhen heated" refers to a material capable of giving off a large amountof the water or carbon dioxide gas present therein on application ofheat at a temperature of not lower than 100° C. The foregoing materialcapable of emitting water, for example when heated to 600° C., can giveoff at least 15% by weight of water based on 100% by weight of watercontained in the material at a temperature of slightly lower than 100°C. (highest temperature at which water does not evaporate). The water iscontained in the material in the form of e.g., absorbed water or waterof crystallization. The foregoing materials capable of giving off carbondioxide gas are those able to emit CO₂ at high temperatures, for examplerelease carbon dioxide when heated to about 900° C. Examples of thematerial capable of emitting water are as follows.

(1) Water containing alumina type materials such as Al(OH)₃, gibbsite,boehmite, diaspore, bayernite, etc.

(2) Alumina silica materials such as allophane, halloysite, unfiredvermiculite, etc.

(3) Magnesia-type materials such as brusite, attapulgite, etc.

(4) Ettringite and like materials.

Typical examples of materials capable of absorbing heat are thosecontaining carbonates such as magnesium carbonate, calcium carbonate,magnesium carbonate calcium carbonate composite materials, etc.

A material capable of giving off water and a material capable ofemitting carbon dioxide gas may be conjointly used. In this case, thematerial capable of releasing water is used preferably in more thanequivalent amount.

When required, the self-hardening composition to be used in the methodof this invention can incorporate a metallic foaming agent and a foamingstabilizer to improve lightweight properties.

Examples of the metallic foaming agent used as the component (D) includevarious metal elements, metal alloys and intermetallic compounds. Usefulmetal elements can be any of those in the Groups IIB, IIIA, IIIB, IVA,IVB, VA, VB, VIB, VIIB and VIII in the Periodic Table. Preferable ofthese elements are those belonging to the third to fifth periods such asCr, Mn, Ti, Zr, V, Si, Ge, Sb, Fe, Co, Ni, Cu, Zn, Al, Ca, Sn, etc.among which Ti, Zr, V, Al, Si, Ge, Sb, Zn and the like are especiallypreferred. Metalloid elements such as B. As and the like are also usablein this invention. Representative examples of useful alloys andintermetallic compounds (metal-to-metal compounds or metal-to-nonmetalcompounds) are Al-Si, Al-Ti, Al-Mn, Al-Cu-Si, Al-Cu, Zn-S, Zn-Sn, Cu-Si,Fe-Si, Si-Ni, Co-Sb, etc. At least one of those exemplified above as thecomponent (D) is usually used in the form of particles, preferably thosehaving a particle size of not greater than 150μ.

Examples of the foaming stabilizer used as the component (E) in thepresent invention are inorganic materials selected from silica gel,zeolite, carbon black, activated carbon, talc, mica, palygorskite andsepiolite, and organic material such as surfactants (other than metallicsoaps), conventional animal proteins and dimethyl silicon derivativesused heretofore as air-entraining agents for cements. Examples of usefulsurfactants are various and include anionic surfactants such as sodiumpolyoxyethylene alkyl sulfonate and sodium alkyl naphthalenesulfonate,cationic surfactants such as lauryltrimethyl ammonium chloride and likequaternary ammonium salts, nonionic surfactants such as polyoxyethyleneglycol oleate and polyoxyethylene glycol laurate, ampholytic surfactantssuch as sodium N-alkyl-β-aminopropionate and polyoxyethylene alkyl etherphosphate, etc. These materials used as the component (E) act touniformly disperse the component (D) in the system and to assurestabilized foaming and are therefore effective in forming uniform pores.The component (E) which is inorganic is used preferably in the form ofparticles having a particle size of not greater than 200μ.

Given below are the proportions of the components (A) to (C) or (A) to(E) for the self-hardening composition to be used in the method of thisinvention.

    ______________________________________                                        Component (A)    100      parts by weight                                     Component (B)    3 to 250 parts by weight                                     Component (C)    20 to 800                                                                              parts by weight                                     Component (D)    0 to 50  parts by weight                                     Component (E)    0 to 200 parts by weight                                     ______________________________________                                    

The proportion of the component (B) ranges about 15 to about 250 partsby weight when the component used is hydraulic cement, silica dust orzinc oxide, but ranges about 3 to about 30 parts by weight, when it isbivalent or higher valent metal salt of higher fatty acid, bivalent orhigher valent metal salt of water-soluble high polymer having carboxyl,acidic metallic oxide, phosphate, borate, sulphate of bivalent metal orsulphite of bivalent metal.

The proportion of the component (C) is preferably 100 to 700 parts byweight, more preferably 300 to 650 parts by weight.

The self-hardening composition of this invention which can be preparedfrom the components (A) to (C) may contain the component (D) to givelightweight properties. The preferred amount of the component (D) rangesfrom 5 to 50 parts by weight. When the component (D) is not used, thefoaming stabilizer, i.e. the component (E), may be omitted althoughunlikely to adversely affect the system with serious result, if used.The amount of the component (E) is about 0 to about 200 parts by weightwhen it is inorganic but is about 0 to about 18 parts by weight when itis organic.

The self-hardening composition to be used in this invention may furthercontain at least one of a fibrous material (component (F)),water-soluble resin (component (G)), and inorganic swelling agent(component (H)). One of these additives, a fibrous material (component(F)), is used to give coatings having the bending strength increased byabout 1.5 times and the shrinkage decreased by about twice. Thecomponent (F) is preferred to give lightweight foamed bodies. The amountof the component (F) is up to about 30 parts by weight per 100 parts byweight of the component (A) (calculated as solids). With an excess ofthe component (F), the composition of this invention has a reducedfluidity and particularly will not foam smoothly. Examples of fibrousmaterials are glass fiber, rock wool, asbestos, carbon fiber, quartzfiber, high silica fiber, aluminum silicate fiber and like inorganicfibers, and cellulose acetate fiber, polyester fiber, acrylic fiber andlike organic fibers. The fibrous materials are used in the form ofstrands such as monofilaments, chopped strands, etc. The water-solubleresin (component (G)) mentioned above as one of the other additives isincorporated mainly to render the composition easier to handle and alsoserves to improve mechanical strength to some degree (20 to 30%). Theamount of the component (G) is not greater than 30 parts by weight(calculated as solids) per 100 parts by weight of the component (A). Anexcess of the component (G) leads to reduction in the water resistanceof the foamed body. Examples of the water-soluble resins arepolyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone and likewater-soluble synthetic resins; methyl cellulose, carboxymethylcellulose and like cellulose ethers; gelatin, gum arabic, sodiumalginate, protein, starch, dextrin and like water-soluble naturalresins; etc. The water soluble resins are used in the form of particlesor as formulated into an aqueous solution.

Inorganic swelling agents can be added as the component (H) in thisinvention. This swelling agent serves to increase the fluidity of thepresent composition and to enhance the operational efficiency. Theamount of the swelling agent is up to about 60 parts by weight per 100parts by weight of the component (A). An excess of the component (H)leads to the composition which foams less smoothly. Examples of usefulswelling agents are kaolin, bentonite, activated clay and like clays,white carbon, water-containing magnesium silicate, etc.

Other additives can be incorporated into the composition of thisinvention. Examples of the other additives include quartz glass,cristobalite, alumina, fly ash, calcium carbonate, siliceous powder,pottery powder, inorganic pigment, lightweight aggregate, etc. Theseadditives are able to impart a lower bulk density and increased volumeto the coating and to achieve reinforcement. Preferred examples oflightweight aggregates are organic and inorganic and include foamedparticles and granules of synthetic resins prepared from vinyl chloride,phenol, urea, styrene, urethane, ethylene or the like, granules orfoamed and pulverized granules of synthetic rubbers, and like organiclightweight aggregates, expanded shale, calcined pearlite, silicaballoon, granular foamed silica and like inorganic lightweightaggregates, shattered foamed lightweight concrete, etc.

The amount of these additives is about 0 to about 100 parts by weightper 100 parts by weight of the component (A).

The foregoing self-hardening composition comprising the above-specifiedamounts of components is mixed with a suitable amount of water and themixture is placed into the specific space.

The self-hardening composition of this invention comprising thecomponents (A), (B) and (C) can be mixed with an air-entraining agent toform a lightweight coating. The amount of the air-entraining agent usedis about 0 to about 50 parts by weight per 100 parts by weight of thecomponent (A). The air-entraining agent may be added to an aqueoussolution of the component (A) and then the components (B) and (C) may beadded thereto to provide a mixture which is allowed to stand. The use ofthe air-entraining agent in this manner results in a lightweight coatingwhich has a bulk specific gravity of at least about 0.7 g/cm³. Althoughthe hardened coating obtained by use of the air entraining agent has amechanical strength a little lower than when using a metallic foamingagent, there is no problem in practical use.

The corner beads are used to give a joint between abutting panel ends inthe corners of the enclosure and to reinforce the corners thereof.Useful corner beads include a variety of those known in the art,preferred examples thereof being those made of stainless steel, aluminumor the like. The corner beads can be attached to the corners of theenclosure in the conventional manner, as with an adhesive or by turningscrews.

Another embodiment of the method according to this invention will bedescribed below in detail with reference to FIG. 2.

FIG. 2 shows an embodiment of the method according to this inventionusing a square steel piece. The reference numerals 1 to 4 represent likemembers in FIG. 1. Indicated at 5 is a square steel piece. No backer 6is used herein. The self-hardening composition is poured into the spaceformed between the square steel piece 5 and the panels 2 in FIG. 2. Theembodiment of FIG. 2 is therefore substantially the same as that usingthe wide-flange steel piece except for the absence of backers 6.

The method of this invention can achieve the following results.

(1) Results attainable by the method of the invention as a whole

(A) The method of the invention can be carried out either inconstruction sites or in refractory coating plants. Particularly themethod of the invention when practiced in the plant gives coatings witha high precision.

(B) The method of the invention provides coatings integrally formed withsteel elements and panels and having a decorated finish.

(C) The method of the invention gives a massive construction having agreat mechanical strength because it is integrally formed of panels,self-hardening composition and steel frame.

(D) The method of the invention can apply coating compositions to thespecific uniform thickness so that fire resistance is exhibitedvirtually evenly throughout the coatings.

(E) Piping and wiring works can be done utilizing the hollow space inthe steel element before application of coatings.

(F) With no spray used, the method of the invention can eliminate thepossibility of staining the environment due to the scatter of thecomposition in application and thus can improve the environment in amarked degree.

(G) The method of the invention does not use an adhesive for applicationover the entire surface of steel elements so that the hardened layer ofself-hardening composition possesses markedly high adherence and waterresistance and thus is unlikely to peel.

(H) The method of the invention can apply layers even to complicatedportions of steel elements in conformity with the shape thereof (whenrequired by spraying or troweling).

(I) The layer formed can harden in a short time to integrally unite withthe panels and the steel element.

(J) The method of the invention can produce layers which are prone todevelop no crack and can apply layers in a shorter time.

Diverse results can be achieved particularly due to the use of theself-hardening composition in this invention. More specifically, thefollowing results stem from the properties peculiar to self-hardeningcompositions.

(K) The layer of the composition of the invention is formed on steelelements with good adherence and will not peel from the steel elementseven when subjected to high temperatures (as in a fire).

(L) The composition of the invention is applied directly to the surfaceof steel elements and can inhibit corrosion itself, thus eliminating theuse of laths and the need for anti-corrosion treatment and consequentlyleading to saving of steps.

(M) The composition of the invention has such a high fire resistancethat the layer formed can be thinner in specific thickness than whenusing conventional refractory compositions. As a result, the totalthickness of the integral construction including that of the decorativepanels (6 to 9 mm in thickness) is smaller than in applying conventionalrefractory compositions. For example, "fired vermiculite plaster" mustbe applied to a column to a thickness of at least 45 mm to form a layercapable of withstanding fire for 2 hours, whereas the composition of theinvention can serve the same purpose by being applied to a thickness of30 to 35 mm (composition) to which is added a thickness of 6 to 9 mm(panels), resulting in combined thickness of about 35 to about 40 mm.

(N) The composition of the invention gives a lightweight refractorylayer.

The method of the present invention will be described below in moredetail with reference to the following Examples.

EXAMPLE 1

A wide-flange section steel column is used which has a height (H) of 300mm, sides (B) of 300 mm, thickness (t₁) of 10 mm, thickness (t₂) of 15mm and length (L) of 4,000 mm as shown in FIG. 3 according to JIS, G3192: "Dimensions, weight and permissible variations of hot rolled steelsections". Starting with one end of the sides as shown in FIG. 4,spacers made of calcium silicate and measuring 20 mm×20 mm×30 mm(height) are adhered with an epoxy resin adhesive to the sides inparallel with one another with spacing of 100 mm between the axes of thetwo spacers. In FIG. 4, the arrows represent the transverse distances onthe sides and the reference numeral 4 indicates the spacers. Thenfurther spacers are adhered to the sides with spacing of 300 mmlongitudinally of the sides as illustrated in FIG. 5 in which the arrowsrepresent the longitudinal direction. Two plaster boards measuring 9mm×280 mm×2,000 mm are each adhered as backers with an epoxy resinadhesive to the interior in the hollow space of the columnlongitudinally thereof as shown in FIG. 6. Two asbestos cement slatesmeasuring 6 mm×372 mm (inside 360 mm)×2,000 mm are adhered with anadhesive to both of the sides longitudinally thereof with the spacersspanning between the column and the panels as shown in FIG. 7. Twopanels of the same type are joined with an adhesive to the heightportion of the column with use of stainless steel corner beads. In thisway, there is formed a shuttering having hollow space surrounding thecolumn. The reference numerals 11, 8, 9 and 10 in FIG. 7 indicate cornerbeads, spacers, column and backers, respectively.

Into a mortar mixer of about 300 l volume was placed 80 kg of an aqueoussolution of sodium silicate having a concentration of 30% by weight andSiO₂ /Na₂ O mole ratio of 2.5. To the solution was added a mixture of 30kg of portland cement (commercially available product having a CaO/SiO₂mole ratio of 2.55) and 120 kg of white gibbsite powder. The resultingmixture was mixed in the mortar mixer to obtain a uniform paste having aspecific gravity of 1.2. The paste was poured into the hollow space inthe shuttering to uniformly fill the space with the paste fully to thelength of 4,000 mm. The paste used amounted to about 190 kg (about 60 kgof the paste was left unused). The paste in the shuttering hardened inabout 2 hours.

The refractory coating thus obtained presented a pleasing appearancebecause of the asbestos cement slates attached to the surface of thecoating. The slates permitted the application of a decorative coatingcomposition commonly used in the art.

Aside from the foregoing experiment, two samples were prepared in thesame manner as above using a wide-flange section steel piece having aheight (H) of 300 mm, side (B) of 300 mm, thickness (t₁) of 10 mm,thickness (t₂) of 7 mm and length (L) of 1,000 mm. The following testswere conducted using the two samples thus prepared with the resultsshown in Table 1 below.

(1) Fire resistance test: a small-scale fire resistance test accordingto the method in JIS A 1304.

(2) Adhesion tests:

(i) After the corner beads were detached, the samples were tested forthe adhesion in the interface between the layer of self-hardeningcomposition and the panels according to the adhesion test in JIS A 6909.

(ii) The layer of self-hardening composition was shaved off to athickness of about 5 mm and checked for the adhesion in the interfacebetween the steel piece and layer according to the adhesion test in JISA 6909.

(3) Test for resistance to saline solutions: The sample shaved asmentioned above in (2), (ii) was immersed in a 5% aqueous solution ofsodium chloride for 7 days. Then the layer of self-hardening compositionwas removed from the steel piece to observe the surface of the steelpiece.

                  TABLE 1                                                         ______________________________________                                                         Result                                                       ______________________________________                                        (1) Fire resistance test                                                      (a) Deteriorative change                                                                         No deteriorative change,                                                      i.e., no abnormality                                       (b) Crack          No crack, i.e., no                                                            abnormality                                                (c) Surface temperature                                                                          230° C.                                             (d) Highest temp. of steel                                                                       380° C.                                             (e) Average temp. of steel                                                                       300° C.                                             (f) Time for remaining                                                                           No remaining flame                                         flame                                                                         (2) Adhesion test                                                                                (i) 1.22 kgf/cm.sup.2 or more                                                 (the slate broken in                                                          its interior)                                                                 (ii) 5.8 kgf/cm.sup.2                                      (3) Test for saline solu-                                                                        No corrosion over the                                      tions              surface of steel piece                                     ______________________________________                                    

EXAMPLES 2 to 11

Small-size samples were prepared in the same manner as in Example 1using a wide-flange section steel piece having a length (L) of 1,000 mmand the same type of self-hardening compositions as used in Example 1except that the components of the kinds as shown below were employed inthe amounts indicated below in Table 3. Table 4 below shows the results.

                                      TABLE 2-1                                   __________________________________________________________________________    Component (A) (Water-soluble alkali metal silicate)                                               SiO.sub.2 /R.sub.2 O*                                                               Conc.                                               No.                                                                              Name of Material mole ratio                                                                          (%) Remark                                          __________________________________________________________________________    A-1                                                                              Aqueous solution of sodium silicate                                                            2.5   30  Product of Osaka Sodium                                                       Silicate Co., Ltd., Japan                       A-2                                                                              Aqueous solution of potassium                                                                  2.0   30  Product of Osaka Sodium                            silicate                   Silicate Co., Ltd., Japan                       __________________________________________________________________________     (Note): *R stands for alkali metal.                                      

                                      TABLE 2-2                                   __________________________________________________________________________    Component (B) (Hardening component)                                                                   Particle                                              No.                                                                              Name of Material                                                                         Composition                                                                             size (μ)                                                                        Remark                                           __________________________________________________________________________    G-1                                                                              Portland cement                                                                          CaO/SiO.sub.2 = 2.55                                                                    5-100                                                                              Product of Denki Kagaku Kogyo                                                 Kabushiki Kaisha, Japan                          C-2                                                                              Alumina cement                                                                           Al.sub.2 O.sub.3 /CaO = 1.57                                                            5-100                                                                              Product of Denki Kagaku Kogyo                                                 Kabushiki Kaisha, Japan                          C-3                                                                              Aluminum phosphate                                                                       Powder    10-50                                                                              Reagent                                          __________________________________________________________________________

                  TABLE 2-3                                                       ______________________________________                                        Component (C) (Bound water-containing material)                                                                  Particle                                   No.  Name of Material                                                                             Composition    size (μ)                                ______________________________________                                        C-1  Gibbsite       Al.sub.2 O.sub.3.3H.sub.2 O                                                                  10-300                                     C-2  Halloysite     Al(Si.sub.2 O.sub.5)(OH).sub.4.2H.sub.2 O                                                    100-500                                    C-3  Aluminum hydroxide                                                                           Al(OH).sub.3   5-100                                      C-4  Magnesium carbonate                                                                          MgCO.sub.3     5-100                                      ______________________________________                                    

                  TABLE 2-4                                                       ______________________________________                                        Component (D) (Metallic Foaming agent)                                             Name of   Particle                                                       No.  Material  size (μ)                                                                             Remark                                               ______________________________________                                        D-1  Fe--Si    5-50      Guaranteed reagent                                   D-2  Al        1-50      Product of Toyo Aluminum Co.,                                                 Ltd., Japan                                          ______________________________________                                    

                  TABLE 2-5                                                       ______________________________________                                        Component (E) (Foaming stabilizer)                                            No.   Name of Material     Particle size (μ)                               ______________________________________                                        E-1   Silica gel           5-50                                               E-2   Polyoxyethylene nonylphenyl ether                                                                  --                                                 ______________________________________                                    

                  TABLE 2-6                                                       ______________________________________                                        Component (F) (Fibrous component)                                             No.     Name of Material                                                                             Fiber (mm)                                                                              Remark                                       ______________________________________                                        F-1     Glass fiber     3        Staple                                       F-2     Polypropylene fiber                                                                          10        Staple                                       ______________________________________                                    

                  TABLE 2-7                                                       ______________________________________                                        Component (G) (Water-soluble resin component)                                 No.     Name of Material  Form                                                ______________________________________                                        G-1     Hydroxyethyl cellulose                                                                          Powder                                              G-2     Polyethylene oxide                                                                              Aqueous solution                                    ______________________________________                                    

                  TABLE 2-8                                                       ______________________________________                                        Component (H) (Inorganic swelling agent)                                      No.     Name of Material   Particle size (μ)                               ______________________________________                                        H-1     Bentonite          5-100                                              H-2     Anhydrous magnesium silicate                                                                     0.5-10                                             ______________________________________                                    

                                      TABLE 3                                     __________________________________________________________________________    Ex. 2    Ex. 3                                                                             Ex. 4                                                                             Ex. 5                                                                             Ex. 6                                                                             Ex. 7                                                                             Ex. 8                                                                             Ex. 9                                                                             Ex. 10                                                                            Ex. 11                               __________________________________________________________________________    No. A-1                                                                            20 kg                                                                             20 kg                                                                             20 kg                                                                             20 kg                                                                             20 kg                                                                             20 kg                                                                             20 kg                                                                               kg                                                                                kg                                                                              10 kg                                No. A-2                          20  20  10                                   No. B-1       7   7   7   7   7   7                                           No. B-2                                                                             7                                   5                                   No. B-3   1                           0.8                                     No. C-1                                                                            30  30          30  30  30  25                                           No. C-2      30                      20                                       No. C-3          15                      20                                   No. C-4          15                      10                                   No. F-1               0.5                                                     No. F-2                                                                       No. G-1                   0.02                                                No. G-2                                                                       No. H-1                       2.5                                             No. H-2                                                                       __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    Ex. 2   Ex. 3                                                                              Ex. 4                                                                              Ex. 5                                                                              Ex. 6                                                                              Ex. 7                                                                              Ex. 8                                                                              Ex. 9                                                                              Ex. 10                                                                             Ex. 11                        __________________________________________________________________________    (1)-1                                                                            No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                        (1)-2                                                                            No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                        (1)-3                                                                            220° C.                                                                     240° C.                                                                     240° C.                                                                     250° C.                                                                     230° C.                                                                     230° C.                                                                     220° C.                                                                     230° C.                                                                     240° C.                                                                     240° C.                (1)-4                                                                            360° C.                                                                     380° C.                                                                     390° C.                                                                     420° C.                                                                     380° C.                                                                     370° C.                                                                     380° C.                                                                     390° C.                                                                     400° C.                                                                     370° C.                (1)-5                                                                            280° C.                                                                     300° C.                                                                     310° C.                                                                     340° C.                                                                     300° C.                                                                     300° C.                                                                     300° C.                                                                     310° C.                                                                     310° C.                                                                     300° C.                (1)-6                                                                            No rf.                                                                             No rf.                                                                             No rf.                                                                             No rf.                                                                             No rf.                                                                             No rf.                                                                             No rf.                                                                             No rf.                                                                             No rf.                                                                             No rf.                        (2)-1                                                                            11.4 13.5 12.0 1.5  12.3 14.1 10.3 12.2 12.4 11.5                             Kgf/cm.sup.2                                                               (2)-2                                                                            4.3  5.4  5.1  4.7  5.2  5.8  4.9  5.5  6.2  5.4                           (3)                                                                              No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                                                                             No ab.                        __________________________________________________________________________     (Note: No ab. stands for no abnormality, and No rf. is short for no           remaining flame.)                                                        

EXAMPLES 12 to 21

These Examples employed the same type of self-hardening compositions asused in Example 1 with the exception of using the components of thekinds, including the metallic foaming agent and foaming stabilizer, asshown below in Table 5. The small-size samples (with wide-flange sectionsteel pieces having a length (L) of 1,000 mm) used in Examples 12 to 21were prepared in the same manner as in Example 1. However, in Example12, tests were carried out using a sample having a wide-flange sectionsteel column with a length (L) of 4,000 mm which was made as follows.The composition was partly poured into the hollow space in theshuttering in an amount sufficient to fill the space to a height ofabout 500 mm. The layer thus formed expanded and hardened in 2 hours toa length of about 1,000 mm. Then the composition was partly poured intothe space in such amount as to fill the space to a height of about 500mm and was left to stand for 2 hours. The same procedure was repeated 4times to provide the steel column having a length of 4,000 mm andsurrounded with a refractory layer. The foamed and hardened body in thehollow space was evenly cellular and extended over the distance of 4,000mm to provide a uniform refractory coating.

Small size samples were prepared from the components in the amountslisted below in Table 5 and tested with the results indicated later inTable 6.

                                      TABLE 5                                     __________________________________________________________________________    Ex. 12   Ex. 13                                                                            Ex. 14                                                                            Ex. 15                                                                            Ex. 16                                                                            Ex. 17                                                                            Ex. 18                                                                            Ex. 19                                                                            Ex. 20                                                                            Ex. 21                               __________________________________________________________________________    No. A-1                                                                            20  20  20  20      20      20      20                                   No. A-2              20      20      25                                       No. B-1                                                                            7   7   7           5   7   7   7   7                                    No. B-2          5                                                            No. B-3              5                                                        No. C-1                                                                            30  30  30          25  25  25  25  25                                   No. C-2          30                                                           No. C-3              30                                                       No. D-1                                                                            0.6     0.5     0.8 0.3     0.8 0.8 0.8                                  No. D-2  0.5     0.5         1.5                                              No. E-1                                                                            4   4               2   6   4   4   4                                    No. E-2      0.1 0.1 0.1                                                      No. F-1                                                                       No. F-2                          0.5                                          No. G-1                                                                       No. G-2                              0.02                                     No. H-1                                                                       No. H-2                                  2.5                                  __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________    Ex. 12    Ex. 13                                                                            Ex. 14                                                                            Ex. 15                                                                            Ex. 16                                                                            Ex. 17                                                                            Ex. 18                                                                            Ex. 19                                                                            Ex. 20                                                                            Ex. 21                              __________________________________________________________________________    Foaming                                                                             30  30  35  40  35  30  30  35  30  30                                  time (min)                                                                    Bulk  0.7 0.8 0.8 0.8 0.6 0.7 0.8 0.9 0.7 0.8                                 specific                                                                      gravity of                                                                    layer                                                                         Uniformity                                                                          Good                                                                              Good                                                                              Good                                                                              Good                                                                              Good                                                                              Good                                                                              Good                                                                              Good                                                                              Good                                                                              Good                                of cells                                                                      (1)-1 No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                              (1)-2 No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                              (1)-3 230° C.                                                                    230° C.                                                                    240° C.                                                                    230° C.                                                                    230° C.                                                                    240° C.                                                                    220° C.                                                                    220° C.                                                                    230° C.                                                                    240° C.                      (1)-4 390° C.                                                                    380° C.                                                                    400° C.                                                                    390° C.                                                                    390° C.                                                                    380° C.                                                                    370° C.                                                                    390° C.                                                                    400° C.                                                                    400° C.                      (1)-5 290° C.                                                                    300° C.                                                                    310° C.                                                                    300° C.                                                                    300° C.                                                                    300° C.                                                                    290° C.                                                                    280° C.                                                                    310° C.                                                                    290° C.                      (1)-6 No rf.                                                                            No rf.                                                                            No rf.                                                                            No rf.                                                                            No rf.                                                                            No rf.                                                                            No rf.                                                                            No rf.                                                                            No rf.                                                                            No rf.                              (2)-1 6.1 5.8 6.2 6.4 4.3 5.7 4.9 6.3 6.1 5.2                                 (2)-2 3.5 4.2 3.8 3.9 2.7 3.5 3.2 4.1 4.3 3.3                                 (3)   No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                                                                            No ab.                              __________________________________________________________________________     (Note: No ab. stands for no abnormality, and No rf. for no remaining          flame.)                                                                  

I claim:
 1. A method for forming a refractory coating on a steel columnor steel beam serving as a structural member of a building, the methodcomprising the steps of (1) adhering panels directly or indirectly tothe surface of the steel column or steel beam with provision for ahollow space between the surface of the steel column or steel beam andthe panels and (2) pouring a pasty self-hardening refractory compositioninto the hollow space in which the composition hardens into a layerintegrally united with the panels and the steel column or steel beam,wherein the self-hardening refractory composition comprises:(A) at leastone water-soluble alkali silicate, (B) a hardener for the water-solublealkali silicate, and (C) at least one material selected from the groupconsisting of a material containing bound water and a material capableof absorbing heat when heated.
 2. A method as defined in claim 1 whereinspacers are attached to the panels and the surface of the column or beambefore placing the self-hardening refractory composition into the space.3. A method as defined in claim 1 or 2 wherein the self-hardeningrefractory composition comprises:water-soluble alkali silicate, ahardener for the water-soluble alkali silicate, a metallic foamingagent, and a foaming stabilizer when required.
 4. A method as defined inclaim 1 wherein in addition to the components (A) to (C), theself-hardening refractory composition further comprises (D) a metallicfoaming agent and (E) a foaming stabilizer when required.